Desktop Replacement - Physical, RDS or VDI?

Having recently gone through the decision making process for replacing our existing desktop infrastructure, I put together a list of considerations/questions that helped me to make a recommendation for our new desktops.

I've grouped the questions under rough headings - the list is not exhaustive, simply the questions I asked;

Applications

What applications do the users need to run?

Do those applications lend themselves to being run in a datacentre?
Can the application run in a terminal server environment?

Application Virtualisation

Is it technically possible to virtualise/stream the apps?
Does everyone need the app or is it only some users?
Does the application need to access locally stored data?
Does the application need to integrate with other applications? If so, where are they?
Does data need to stay off the client device?

Costs

What licencing is required? How much will it cost?
What end-user equipment is required? Are there different options? How much will it cost?
What back-end equipment is required? Are there different options? How much will it cost?

Support

What difficulties are there in providing remote support to users?
What potential end-user hardware issues are there? (Device fails/user reset to factory)

Long Term

How often will we need to refresh the hardware?
How will we go about software updates and patching?

Network

In a multi-site environment, are the network links between sites able to support everything we want the infrastructure to do?